Passenger protection system

ABSTRACT

A passenger protection system includes: a sensor outputting a detection digital data corresponding to collision; a passenger protection device; and an ECU. The sensor outputs a bit sequence providing an important bit group. A memory stores the data and the sequence doubly for storing first and second detection digital data and first and second bit sequences. The ECU determines based on the first or second data whether it is necessary to protect the passenger when the first data is equal to the second data. When the first data is different from the second data, and the first sequence is equal to the second sequence, the ECU replaces the important bit group in the first or second data with the first or second sequence, and determines based on the first or second data after replacement.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2009-66089filed on Mar. 18, 2009, the disclosure of which is incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to a passenger protection system.

BACKGROUND OF THE INVENTION

Conventionally, a passenger protection system includes a sensor foroutputting a detection data corresponding to an amount of impact when anobject collides with a vehicle, a passenger protection device forprotecting a passenger of the vehicle from collision, and a ECU forcontrolling the passenger protection device. In the system, the ECUdetermines based on the detection data from the sensor whether it isnecessary to protect the passenger from occurrence of the collision.When the ECU determines that it is necessary to protect the passengerfrom collision, the ECU controls the passenger protection device. Thissystem is described in, for example, JP-A-2007-8392.

However, in the above case, bit fixation may occur at a specific bit ina memory medium in the ECU for storing the detection data received fromthe sensor. Thus, collision determination may be incorrect.

In view of the above difficulty, the present inventor has studied asystem. Specifically, to reduce the possibility of failure ofdetermination that it is necessary to protect the passenger fromcollision, as shown in FIG. 7, detection data 52 output from a sensor 51is stored in two different portions 54, 55 in a ECU 53. Then, two datain the portions 54, 55 are compared with each other. When the two dataare not the same, the system determines malfunction, and then, thesystem deletes the two data.

Thus, the system reduces the possibility of failure of determination.However, function of the passenger protection system for detectingcollision to protect the passenger may be reduced.

SUMMARY OF THE INVENTION

In view of the above-described problem, it is an object of the presentdisclosure to provide a passenger protection system with high detectionaccuracy. Specifically, in the system, possibility of malfunction ofdetermination of collision is reduced, and the system surely detectscollision in order to protect a passenger from the collision.

According to an aspect of the present disclosure, a passenger protectionsystem for a vehicle includes: a sensor for detecting an impact ofcollision when the vehicle collides with an object and for outputting adetection digital data corresponding to a magnitude of the impact; apassenger protection device for protecting a passenger from thecollision; and an electric control unit for determining based on thedetection digital data whether it is necessary to protect the passengerfrom the collision and for activating the passenger protection devicewhen the electric control unit determines that it is necessary toprotect the passenger from the collision. The sensor outputs a bitsequence together with the detection digital data to the electriccontrol unit. The bit sequence includes a plurality of bits, whichprovide an important bit group. The important bit group is defined insuch a manner that difference of the magnitude of the impact between acase where one bit of the detection digital data is “1” and a case wherethe one bit of the detection digital data is “0” is equal to or largerthan a predetermined value. The detection digital data includes aplurality of bits for providing the important bit group. The electriccontrol unit includes a memory. The memory stores the detection digitaldata doubly so that a first detection digital data and a seconddetection digital data are stored in the memory. The memory stores thebit sequence doubly so that a first bit sequence and a second bitsequence are stored in the memory. The electric control unit determinesbased on the first or second detection digital data whether it isnecessary to protect the passenger from the collision when the firstdetection digital data is equal to the second detection digital data.When the first detection digital data is different from the seconddetection digital data, the electric control unit compares the first bitsequence with the second bit sequence. When the first detection digitaldata is different from the second detection digital data, and the firstbit sequence is different from the second bit sequence, the electriccontrol unit does not determine whether it is necessary to protect thepassenger from the collision. When the first detection digital data isdifferent from the second detection digital data, and the first bitsequence is equal to the second bit sequence, the electric control unitreplaces the important bit group in the first or second detectiondigital data with the first or second bit sequence, and the electriccontrol unit determines based on the first or second detection digitaldata after replacement whether it is necessary to protect the passengerfrom the collision.

In the above system, even if the first detection data is different fromthe second detection data, the system determines with using the modifiedfirst oir second detection data whether it is necessary to protect thepassenger from the collision. Thus, the system surely detects collisionin order to protect a passenger from the collision. Further, possibilityof malfunction of determination of collision is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a diagram showing a passenger protection system according toan example embodiment;

FIG. 2 is a diagram showing a transmit data of a sensor;

FIG. 3 is a diagram showing the sensor;

FIG. 4 is a diagram showing a A/D conversion process in a A/D converter;

FIG. 5 is a diagram showing an air bag ECU;

FIG. 6 is a flowchart showing a process executed by a CPU in the air bagECU; and

FIG. 7 is a diagram showing a passenger protection system as acomparison example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a passenger protection system mounted on a vehicle 10. Thesystem detects collision of the vehicle 10 with an object. Based ondetection result of the collision, the system functions to protect apassenger of the vehicle 10 from the collision.

Specifically, the system includes a sensor 1, an air bag 2 as one ofexamples of passenger protection, devices, and an air bag ECU 3.

The sensor 1 detects impact of the collision when the vehicle 10collides with the object. The sensor transmits digital data as atransmit data corresponding to a magnitude of the detected impact. Thesensor 1 may be an acceleration sensor. The sensor 1 detectsacceleration to be applied to the sensor 1, and the accelerationcorresponds to the magnitude of the impact. When the accelerationdetected by the sensor 1 is large, the impact of the collision is large.

The sensor 1 may detects the acceleration in a front direction of thevehicle 10. Alternatively, the sensor 1 may detect the acceleration in aleft direction of the vehicle 10 when the sensor 1 is mounted on a rightside of the vehicle 10. Alternatively, the sensor 1 may detect theacceleration in a right direction of the vehicle 10 when the sensor 1 ismounted on a left side of the vehicle 10.

When the air bag 2 receives an inflation signal from the air bag ECU 3,the air bag 2 inflates so that the air bag 2 catches the passenger, whosits down a seat of the vehicle 10. Thus, the air bag 2 protects thepassenger from the impact of the collision.

The air bag ECU 3 receives the transmit data from the sensor 1. Based onthe received transmission data, the air bag ECU 3 determines whether itis necessary to protect the passenger from the collision. Specifically,the air bag ECU 3 determines whether the collision occurs so that it isnecessary to protect the passenger. This determination is defined ascollision determination. When the ECU 3 determines that the impact isapplied to the vehicle 10, the impact requires protection of thepassenger, the ECU 3 outputs an inflation signal as an activation signalto the air bag 2.

The transmit data 4 to be transmitted from the sensor 1 to the air bagECU 3 will be explained with reference to FIG. 2. The data 4 is one dataframe including a G data 41 as one of detection data and an expanded bitsequence 42. The G data 41 includes a digital data, which shows theacceleration detected by the sensor 1. The expanded bit sequence 42includes a bit group having the same value as a part of bit group ionthe digital data.

More specifically, the G data 41 is a 10-bit digital data, and theexpanded bit sequence 42 is a 4-bit digital data. The 10-bit digitaldata in the G data 41 represents the acceleration detected by the sensor1 so that the acceleration is shown in 10 bits. The expanded bitsequence 42 has the same value as the most significant 4-bit data (i.e.,the highest order 4-bit data) in the G data 41.

The sensor 1 for transmitting the transmit data 4 will be explained withreference to FIG. 3. The sensor 1 includes a transmitting/receivinginterface (i.e., transmitting/receiving I/F) 11, an analog outputelement 12, an AD converter 13, a buffer element 14, a multi-plexer(MPX) 15 and a controller 16.

The interface 11 is an interface circuit for executing datacommunication with the air bag ECU 3. Specifically, the interface 11converts the data output from the multi-plexer 15 with using apredetermined voltage level. Then, the interface 11 transmits theconverted data as one batch of a data frame to the ECU 3. The interface11 receives data from the ECU 3, and then, the interface 11 converts thedata with using a predetermined voltage level. Further, the interface 11outputs the converted data to the controller 16.

The analog output element 12 is a conventional circuit for detectingacceleration. The element 12 outputs an analog signal corresponding tothe detected acceleration to the AD converter 13.

When the AD converter 13 receives a conversion instruction form thecontroller 163, the converter 13 converts the analog signal from theanalog output element 12 into a 10-bit digital data. Then, the converter13 outputs the 10-bit digital data as the converted data to the bufferelement 14. Thus, the 10-bit digital data is the G data 41.

The A/D conversion process in the A/D converter 13 will be explainedwith, reference to FIG. 4. For example, when the range of theacceleration to be output from the analog output element 12 is in arange between −100G and +100G, the converter 13 divides the rangebetween −100G and +100G into multiple segments at regular intervals. Thenumber of segments is 2¹⁰−1=1023. One end of one segment is defined asthe number in a range between 0000000000 and 1111111111, whichcorrespond to −100G and +100G, respectively. Specifically, ends of thesegments are numbered in ascending order from 0000000000 to 1111111111,which are described in 10-bit binary number representation.

The converter 13 outputs one of 10-bit binary digits, which is thenearest value of the acceleration, to the buffer element 14. Thus, theconverter 13 outputs the one 10-bit binary digit as the digital data forexpressing the acceleration.

When the buffer element 14 having the memory medium receives a storinginstruction from the controller 16, the buffer element 14 stores the10-bit digital data (i.e., the one 10-bit binary digit) output from theconverter 13 in a predetermined memory area of the memory medium.

The multi-plexer 15 reads out a value in certain bit of the 10-bitdigital data in order, the certain bit is instructed by the controller16. The multi-plexer 15 outputs the read value of the bit to theinterface 11 in order. Specifically, the multi-plexer 15 forms a serialdata, which consists of values of bits of the 10-bit digital data storedin the buffer element 14. The multi-plexer 15 outputs the formed serialdata to the interface 11.

The controller 16 is a conventional microcomputer including a CPU, aRAM, a ROM and the like. The CPU executes a program stored in the ROM,so that the controller 16 performs various processes. Specifically, thecontroller 16 controls the converter 13, the buffer element 14 and themulti plexer 15 with appropriate timing according to a command receivedfrom the air bag ECU 3 via the interface 11.

Specifically, when the controller 16 receives a command for requiringthe transmit data 4 from the ECU 3, the controller 16 waits for apredetermined transmit timing. When the predetermined transmit timingcomes, the controller 16 outputs the conversion instruction to theconverter 13. Then, the controller 16 outputs a storing instruction tothe buffer element 14. Then, the converter 13 converts the analogacceleration value output from the analog output element 12 into the10-bit digital data. Then, the buffer element 14 stores the 10-bitdigital data in the predetermined memory area.

Further, the controller 16 outputs an instruction to the multi plexer15, the instruction for outputting all of the values of 10 bits from themost significant bit (the highest order bit) to the least significantbit (the lowest order bit) in this order. Then, the controller 16outputs an instruction for outputting a part of the values of the bitsin descending order. Specifically the part of the values of the bits isthe top four bit values so that the part of the bits is in a rangebetween the most significant bit and the fourth most significant bit.Here, the part of the bits may be in a range between the mostsignificant bit and a predetermined ordinal number most significant bitso that the instruction provides to output the part of the values of thebits in a range between the most significant bit and a predeterminedordinal number most significant bit in this order. Thus, themulti-plexer 15 outputs the serial data to the interface 11, the serialdata comprising the first bit, the second bit, the third bit, the fourthbit, the fifth bit, the sixth bit, the seventh bit, the eighth bit, theninth bit, the tenth bit, the first bit, the second bit, the third bitand the fourth bit, which are stored in the buffer element 14.

The interface 11 transmits the serial data as the transmit data 4 to theair bag ECU 3, the serial data being output from the multi-plexer 15. Inthe serial data, the first 10 bit data provide the G data 41, and therest 4 bit data provide the expanded bit sequence 42.

Next, the process of the air bag ECU 3 for processing the transmit data4 will be explained with reference to FIG. 5. The ECU 3 includes acommunication IC 31 as a communication circuit and a control element 32.The communication IC 31 and the control element 32 are connected with atleast three signal passages as a signal line 33 a-33 c.

The communication IC 31 is an interface circuit for performing datacommunication with the sensor 1. Specifically, when the communication IC31 receives a command for the sensor 1 from the control element 32 viathe third passage 33 c, the command which requests the transmit data 4and is output from the control element 32, the IC 31 converts thecommand signal with using a predetermined voltage level. Then, the IC 31transmits the converted command signal to the sensor 1. Here, the thirdpassage 33 c is used for the command.

The IC 31 includes four memory mediums such as registers 31 a-31 d. Whenthe IC 31 receives the transmit data 4 from the sensor 1, the IC 31stores the G data 41 of the transmit data 4 in both of the first G datamemory medium 31 a (i.e., the first G data memory) and the second G datamemory medium 31 b (i.e., the second G data memory), and the IC 31stores the expanded bit sequence 42 in both of the first expanded bitsequence memory medium 31 c (the first bit sequence memory) and thesecond expanded bit sequence memory medium 31 d (the second bit sequencememory).

When the communication IC 31 receives a data acquisition signal from thecontrol element 32 via the third passage 33 c, the IC 31 outputs thedata in the first bit sequence memory 31 c and the data in the first Gdata memory 31 a to the control element 32 via the first passage 33 a.Further, the IC 31 outputs the data in the second bit sequence memory 31d and the data in the second G data memory 31 b to the control element32 via the second passage 33 b.

The control element 32 is a conventional microcomputer having a CPU, aRAM, a ROM and the like. The CPU executes a program stored in the ROM sothat various processes are performed. Specifically, the control element32 outputs the command for the sensor 1 to request the transmit data 4to the communication IC 31 via the first passage 33 a at predeterminedintervals. Then, the control element 32 executes a process shown in FIG.6.

In the process in FIG. 6, the control element 32 obtains the transmitdata 4 via two passages 33 a, 33 b in step S110. Specifically, thecontrol element 32 outputs the data acquisition signal to thecommunication IC 31 via the first passage 33 a. After the controlelement 32 outputs the data acquisition signal, the control element 32obtains the transmit data 4 stored in two different memories 31 a-31 dof the IC 31 via two passages 33 a, 33 b. The data 4 is transmitted fromthe sensor 1.

The G data 41 obtained from the first G data memory 31 a via the firstpassage 33 a is defined as the first G data 41, and the G data 41obtained from the second G data memory 31 b via the second passage 33 bis defined as the second G data 41. The expanded bit sequence 42obtained from the first bit sequence memory 31 c via the first passage33 a is defined as the first expanded bit sequence 42, and the expandedbit sequence 42 obtained from the second bit sequence memory 31 d viathe second passage 33 b is defined as the second expanded bit sequence42.

In step S120, the control element 32 determines whether the first G data41 is equal to the second G data. When the control element 32 determinesthat the first G data 41 is equal to the second G data, it goes to stepS130. When the control element 32 determines that the first G data 41 isnot equal to the second G data, it goes to step S140.

When the first G data is different from the second G data, bit fixationmay occur at the first G data memory 31 a and the first passage 33 a,and/or bit fixation may occur at the second G data memory 31 b and thesecond passage 33 b since the first G data and the second G data arederived from the same original G data and stored in different twomemories 31 a, 31 b. The bit fixation is phenomenon such that a specificbit data of data stored in or output from a device is fixed to aspecific value because of some sort of cause. In this case, the specificbit data in the data output from the control element 32 becomes constantat any time.

In step S130, the acceleration provided by the first G data or thesecond G data is used as the detected acceleration of the sensor 1.Then, the sensor 1 determines whether the detected acceleration is equalto or larger than a predetermined threshold. When the sensor 1determines that the detected acceleration is equal to or larger than apredetermined threshold, the sensor 1 determines that collision occursso that it is necessary to protect the passenger from the collision. Inthis case, the sensor 1 outputs the activation signal to the air bag 2.After that, the process in FIG. 6 ends. When the sensor 1 determinesthat the detected acceleration is smaller than the predeterminedthreshold, the process in FIG. 6 ends.

In step S140, the control element 32 determines whether the firstexpanded bit sequence 42 is equal to the second expanded bit sequence42. When the control element 32 determines that the first expanded bitsequence 42 is equal to the second expanded bit sequence 42, it goes tostep S160. When the control element 32 determines that the firstexpanded bit sequence 42 is not equal to the second expanded bitsequence 42, it goes to step S150.

In step S150, the control element 32 discards the data. Specifically,the element 32 completes the process in FIG. 6 without performingcollision determination with using the first and/or second G data. Inthis case, since the first G data is different from the second G data,and, in addition, the first expanded bit sequence is different from thesecond expanded bit sequence, reliability of the data is very low, andtherefore, the data cannot be used for collision determination.

In step S160, the element 32 recreates the first or second G data withusing the first or second expanded bit sequence. For example, when thesecond G data is recreated with using the first expanded bit sequence, apart of the bit data of the second G data that is also provided by theexpanded bit sequence 42 is replaced with the first expanded bitsequence. In the present embodiment, the highest order bit data, and thesecond to fourth highest order bit data in the second G data arereplaced with the first expanded bit sequence data.

This is because the reliability of the first and second expanded bitsequences is higher than the reliability of the first to fourth highestorder but data in the first and second G data since the first expandedbit sequence is equal to the second expanded bit sequence.

In step S160, the acceleration provided by the recreated G data is usedfor the detected acceleration of the sensor 1. The recreated G data isprepared by the element 32 after replacement. In the above example, therecreated G data is prepared from the second G data. Then, the sensor 1determines whether the detected acceleration is equal to or larger thana predetermined threshold. When the sensor 1 determines that thedetected acceleration is equal to or larger than a predeterminedthreshold, the sensor 1 determines that collision occurs so that it isnecessary to protect the passenger from the collision. In this case, thesensor 1 outputs the activation signal to the air bag 2. After that, theprocess in FIG. 6 ends. When the sensor 1 determines that the detectedacceleration is smaller than the predetermined threshold, the process inFIG. 6 ends.

Thus, the collision determination in step S160 with using the recreatedG data since at least the reliability of replaced bit data in therecreated G data is high. Since the replaced bit data is thepredetermined number of high bit data, i.e., the first to fourth highestbit data, the replaced bit data affects on the collision determinationresult largely, compared with other bit data. Actually, the other bitdata other than the predetermined number of high bit data may affectmerely on consumption of current and/or radiation noise. Accordingly,when the recreated G data is used, the collision determination isperformed with using the G data, which has high reliability in a part ofthe G data that affects largely on the collision determination result.

The above predetermined threshold, which is used for determination ofoccurrence of the collision that requires protection of the passenger ofthe vehicle, may be defined as a 10-bit data such that bit data otherthan the first to fourth highest order bit data is zero. For example,the 10-bit data of the threshold may be one of “1111000000,”“1101000000,” “1001000000,” “0101000000,” and “1110000000.” In thiscase, the threshold has the same data structure as the G data 41, i.e.,the threshold is defined as the 10-bit data, and the G data 41 is alsodefined as the 10-bit data.

Thus, in step S160, only the replaced part of the G data, which isreplaced with the expanded bit sequence, affects on the collisiondetermination result. And, the other part of the G data does notcompletely affect on the collision determination result. Thus,determination accuracy is much improved.

In the passenger protection system, the G data 41 defined as 10-bit datafor showing the detected acceleration in the sensor 1 together with theexpanded bit sequence 42 composed of the first to fourth highest orderbit data are transmitted as one data frame.

The ECU 3 stores the received G data in two different memories 31 a, 31b such that the first G data and the second G data are respectivelystored in the memories 31 a, 31 b. Specifically, the ECU 3 stores the Gdata doubly. Further, the ECU 3 stores the received expanded bitsequence 42 in two different memories 31 c, 31 d such that the firstexpanded bit sequence and the second expanded bit sequence arerespectively stored in the memories 31 c, 31 d. Specifically, the ECU 3stores the expanded bit sequence doubly.

The control element 32 in the ECU 3 obtains the first and second G datavia two different passages 33 a, 33 b, respectively. Further, thecontrol element 32 in the ECU 3 obtains the first and second expandedbit sequences via two different passages 33 a, 33 b, respectively.

When the first G data is equal to the second G data, i.e., when thedetermination in step S120 is “YES,” the collision determination step isperformed with using the first or second G data, i.e., the first orsecond G data is compared with the threshold. When the first G data isdifferent from the second G data, i.e., when the determination in stepS120 is “NO,” the element 32 compares the first expanded bit sequencewith the second expanded bit sequence. When the first expanded bitsequence is different from the second expanded bit sequence, the firstand second G data is not used for the collision determination step. Whenthe first expanded bit sequence is equal to the second expanded bitsequence, the first to fourth highest order bit data in the first orsecond G data is replaced with the first or second expanded bitsequence. Then, the replaced first or second G data is compared with thethreshold. Here, the first to fourth highest order bit data correspondto the most significant bit data group.

Thus, even if the first G data is partially different from the second Gdata, when the first expanded bit sequence is equal to the secondexpanded bit sequence, the G data is modified with using one of thefirst and second expanded bit sequences. The first and second expandedbit sequences are in the most important bit group for collisiondetermination. Then, the modified G data is used for collisiondetermination. Thus, even if the first G data is partially differentfrom the second G data, the collision determination is performed withoutstopping collision determination with using the first and second G dataafter the most important bit grouping the G data, which largely affectson the collision determination result, is replaced with the expanded bitsequence. In this case, the expanded bit sequence is high reliable data.Thus, the detection of collision is performed sufficiently. The systemreduces the possibility of failure of determination. Further, functionof the passenger protection system for detecting collision to protectthe passenger is not reduced.

In the above embodiment, it is not necessary to transmit the transmitdata 4 again from the sensor 1. Specifically, the sensor 1 transmits thesame transmit data 4 only once. Since the sensor 1 does not transmit thesame data 4 again, transmission control of the sensor 1 is simplified.Specifically, it is not necessary to add a resend bit data in thetransmit data 4. Further, it is not necessary to add a register forstoring the resend bit in order to control a resending step.

Other Embodiments

In the above embodiment, the analog acceleration value output from theanalog output element 12 in a range between −100G and +100G is convertedto the G data 41 provided by the 10-bit data in a range between“0000000000” and “1111111111.” Alternatively, the analog accelerationvalue may be converted in a different manner.

For example, the value may be converted to a 10-bit binary numberrepresentation such that −100G corresponds to 1111111111, and +100Gcorresponds to 0000000000, and the value is associated with the 10-bitbinary number representation in descending order. In this case, a partof bits that affects largely on the collision determination is the highbit data. Thus, the expanded bit sequence 42 includes a predeterminednumber of high bit data in a range between the highest bit data and apredetermined ordinal number highest bit.

In some cases where the analog acceleration value is converted to thedigital data in a different manner from the above case, the part of bitsthat affects largely on the collision determination may not be the highbit data.

For example, the analog acceleration value is converted to a 10-bit datain a range between “0000000000” and “1111111111,” and after that, the10-bit data is stored in the buffer element 11. The multi-plexer 15retrieves the 10-bit data in an order from the lowest bit data to thehighest bit data, and the multi-plexer 15 outputs the retrieved data asthe serial data to the interface 11. In this case, a part of bits thataffects largely on the collision determination is the low bit data.Specifically, the part of the serial data that affects largely on thecollision determination is the first to fourth lowest bit data.

In the present embodiment, a part of the bits that affects largely oncollision determination is a bit sequence including multiple bit data,which are defined such that the analog acceleration value is largelychanged when one of the multiple bit data is changed from “1” to “0,” orchanged from “0” to “1.”

For example, the difference of the corresponding analog accelerationvalue between a case where the highest order bit data is “1” and a casewhere the highest order bit data is “0” is calculated as200G/1023×512≈100G, and thus, the difference is 100G. The difference ofthe corresponding analog acceleration value between a case where thelowest order bit data is “1” and a case where the lowest order bit datais “0” is calculated as 200G/1023≈0.20G, and thus, the difference is0.20G.

When the highest bit data in the G data may represent a sign bit showinga positive or negative in the analog acceleration value. In this case,the difference of the corresponding analog acceleration value between acase where the highest order bit data is“1” and a case where the highestorder bit data is“0” is 200G at a maximum. Thus, the correspondinganalog acceleration value is changed by 200G.

In view of the above point, in the present embodiment, even when theanalog acceleration value is converted to the G data as a digital datain a different manner, the most important bit group is defined such thatthe corresponding analog acceleration value is largely changed when thebit data of the most important bit group is changed from “1” to “0,” orfrom “0” to “1.” The expanded bit sequence 42 includes at least the mostimportant bit group.

The control element 32 in the air bag ECU 3 may store information in theROM preliminary, the information about the bit data larger than thethreshold and the bit data smaller than the threshold in accordance witha conversion method of the analog acceleration value to the G data. Insteps S130, S160, based on the information, the G data and the thresholdmay be compared.

As long as the sensor 1 outputs the digital data corresponding to theamount of magnitude of impact of the collision, the sensor 1 may beanother sensor such as a pressure sensor and a displacement sensor. Forexample, the pressure sensor detects pressure to be applied to a body ofthe vehicle corresponding to the magnitude of the impact of collision.The displacement sensor detects a displacement of a body of the vehiclecorresponding to the magnitude of the impact of collision. When thepressure and the displacement are large, the magnitude of impact ofcollision is large.

The expanded bit sequence 42 may be different from a 4-bit data.Alternatively, the G data 41 may be different from a 10-bit data.

The passenger protection device may be different from the air bag 2. Forexample, the passenger protection device for protecting the passengerfrom the impact of collision may be a seat belt pre-tensioner or thelike.

The G data 41 and the expanded bit sequence 42 are transmitted as onebatch data packet so that the G data 41 and the expanded bit sequence 42are disposed in the same frame. Alternatively, the G data 41 and theexpanded bit sequence 42 may be included in different frames,respectively. In this case, the G data 41 and the expanded bit sequence42 are transmitted as separated data packets.

The first expanded bit sequence 31 c is output to the control element 32via the first passage 33 a, which is the same as the first G data 31 a.Alternatively, the first expanded bit sequence 31 c may be output to thecontrol element 32 via a passage (a signal line), which is differentfrom the first passage 33 a of the first G data 31 a and the secondpassage 33 b of the second G data 31 b and the second expanded bitsequence 31 d. The second expanded bit sequence 31 d is output to thecontrol element 32 via the second passage 33 b, which is the same as thesecond G data 31 b. Alternatively, the second expanded bit sequence 31 dmay be output to the control element 32 via a passage (a signal line),which is different from the first passage 33 a of the first G data 31 aand the first expanded bit sequence 31 c and the second passage 33 b ofthe second G data 31 b.

The threshold for determining collision in step S130 may be differentfrom the threshold for determining collision in step S160.Alternatively, the threshold for determining collision in step S130 maybe equal to the threshold for determining collision in step S160.

The first and second G data and the first and second expanded bitsequences may be stored in the same memory medium of the air bag ECU 3such that they are stored in different area of the same memory medium.

In the above embodiment, when the first detection data as the first Gdata is different from the second detection data as the second G data,the first bit sequence as the first expanded bit sequence is comparedwith the second bit sequence as the second expanded bit sequence. Whenthe first bit sequence is equal to the second bit sequence, the mostimportant bit group in the first or the second detection data isreplaced with the first or second bit sequence. Based on comparisonresult between the replaced detection data and the threshold, the ECU 3determines whether collision that requires passenger protection occurs.

A method for determining whether the collision occurs so that it isnecessary to protect the passenger may be different from a case wherethe replaced detection data is compared with the threshold. For example,the replaced detection data may be integrated with time, and theintegrated detection data is compared with the threshold. Based oncomparison result between the integrated detection data and thethreshold, the ECU 3 determines whether collision occurs so that it isnecessary to protect the passenger. Alternatively, the replaceddetection data may be filtered with a low pass filter, so that thefiltered detection data is compared with the threshold.

Each process that is realized by performing a program with thecontroller 16 of the sensor 1 or the CPU 32 of the air bag ECU 3 may berealized by a hard ware such as a FPGA capable of programming a circuitfunction

The above disclosure has the following aspects.

According to an aspect of the present disclosure, a passenger protectionsystem for a vehicle includes: a sensor for detecting an impact ofcollision when the vehicle collides with an object and for outputting adetection digital data corresponding to a magnitude of the impact; apassenger protection device for protecting a passenger from thecollision; and an electric control unit for determining based on thedetection digital data whether it is necessary to protect the passengerfrom the collision and for activating the passenger protection devicewhen the electric control unit determines that it is necessary toprotect the passenger from the collision. The sensor outputs a bitsequence together with the detection digital data to the electriccontrol unit. The bit sequence includes a plurality of bits, whichprovide an important bit group. The important bit group is defined insuch a manner that difference of the magnitude of the impact between acase where one bit of the detection digital data is “1” and a case wherethe one bit of the detection digital data is “0” is equal to or largerthan a predetermined value. The detection digital data includes aplurality of bits for providing the important bit group. The electriccontrol unit includes a memory. The memory stores the detection digitaldata doubly so that a first detection digital data and a seconddetection digital data are stored in the memory. The memory stores thebit sequence doubly so that a first bit sequence and a second bitsequence are stored in the memory. The electric control unit determinesbased on the first or second detection digital data whether it isnecessary to protect the passenger from the collision when the firstdetection digital data is equal to the second detection digital data.When the first detection digital data is different from the seconddetection digital data, the electric control unit compares the first bitsequence with the second bit sequence. When the first detection digitaldata is different from the second detection digital data, and the firstbit sequence is different from the second bit sequence, the electriccontrol unit does not determine whether it is necessary to protect thepassenger from the collision. When the first detection digital data isdifferent from the second detection digital data, and the first bitsequence is equal to the second bit sequence, the electric control unitreplaces the important bit group in the first or second detectiondigital data with the first or second bit sequence, and the electriccontrol unit determines based on the first or second detection digitaldata after replacement whether it is necessary to protect the passengerfrom the collision.

In the above system, even if the first detection data is different fromthe second detection data, the system determines with using the modifiedfirst oir second detection data whether it is necessary to protect thepassenger from the collision. Thus; the system surely detects collisionin order to protect a passenger from the collision. Further, possibilityof malfunction of determination of collision is reduced.

Alternatively, when the first detection digital data is different fromthe second detection digital data, and the first bit sequence is equalto the second bit sequence, the electric control unit may compare thefirst or second detection digital data after replacement with apredetermined threshold digital data. The electric control unitdetermines that it is necessary to protect the passenger from thecollision when the first or second detection digital data afterreplacement is equal to or larger than the predetermined thresholddigital data. All of bit values in the predetermined threshold digitaldata other than the important bit group are “0.” In this case, detectionaccuracy is improved.

Alternatively, the memory may include a first detection digital datamemory, a second detection digital data memory, a first bit sequencememory and a second bit sequence memory. The memory stores the detectiondigital data doubly in such a manner that the first detection digitaldata is stored in the first detection digital data memory, and thesecond detection digital data is stored in the second detection digitaldata memory. The memory stores the bit sequence doubly in such a mannerthat the first bit sequence is stored in the first bit sequence memory,and the second bit sequence is stored in the second bit sequence memory.The electric control unit retrieves the first detection digital datafrom the first detection digital data memory via a first data passage,and the electric control unit retrieves the second detection digitaldata from the second detection digital data memory via a second datapassage when the electric control unit compares the first detectiondigital data with the second detection digital data. The electriccontrol unit retrieves the first bit sequence from the first bitsequence memory via the first data passage, and the electric controlunit retrieves the second bit sequence from the second bit sequencememory via the second data passage when the electric control unitcompares the first bit sequence with the second bit sequence.

Further, the sensor may output the bit sequence together with thedetection digital data as one data frame. The detection digital data isa 10-bit data, and the bit sequence is a 4-bit data.

Furthermore, the sensor may be an acceleration sensor, a pressure sensoror a displacement sensor, and the passenger protection device may be anair bag device or a seat belt pretensioner.

Further, when the first detection digital data is different from thesecond detection digital data, and the first bit sequence is equal tothe second bit sequence, the electric control unit may compare the firstor second detection digital data after replacement with a predeterminedthreshold digital data. The electric control unit determines that it isnecessary to protect the passenger from the collision when the first orsecond detection digital data after replacement is equal to or largerthan the predetermined threshold digital data. All of bit values in thepredetermined threshold digital data other than the important bit groupare “0.”

While the invention has been described with reference to preferredembodiments thereof, it is to be understood that the invention is notlimited to the preferred embodiments and constructions. The invention isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, which arepreferred, other combinations and configurations, including more, lessor only a single element, are also within the spirit and scope of theinvention.

1. A passenger protection system for a vehicle comprising: a sensor fordetecting an impact of collision when the vehicle collides with anobject and for outputting a detection digital data corresponding to amagnitude of the impact; a passenger protection device for protecting apassenger from the collision; and an electric control unit fordetermining based on the detection digital data whether it is necessaryto protect the passenger from the collision and for activating thepassenger protection device when the electric control unit determinesthat it is necessary to protect the passenger from the collision,wherein the sensor outputs a bit sequence together with the detectiondigital data to the electric control unit, wherein the bit sequenceincludes a plurality of bits, which provide an important bit group,wherein the important bit group is defined in such a manner thatdifference of the magnitude of the impact between a case where one bitof the detection digital data is “1” and a case where the one bit of thedetection digital data is “0” is equal to or larger than a predeterminedvalue, wherein the detection digital data includes a plurality of bitsfor providing the important bit group, wherein the electric control unitincludes a memory, wherein the memory stores the detection digital datadoubly so that a first detection digital data and a second detectiondigital data are stored in the memory, wherein the memory stores the bitsequence doubly so that a first bit sequence and a second bit sequenceare stored in the memory, wherein the electric control unit determinesbased on the first or second detection digital data whether it isnecessary to protect the passenger from the collision when the firstdetection digital data is equal to the second detection digital data,wherein, when the first detection digital data is different from thesecond detection digital data, the electric control unit compares thefirst bit sequence with the second bit sequence, wherein, when the firstdetection digital data is different from the second detection digitaldata, and the first bit sequence is different from the second bitsequence, the electric control unit does not determine whether it isnecessary to protect the passenger from the collision, and wherein, whenthe first detection digital data is different from the second detectiondigital data, and the first bit sequence is equal to the second bitsequence, the electric control unit replaces the important bit group inthe first or second detection digital data with the first or second bitsequence, and the electric control unit determines based on the first orsecond detection digital data after replacement whether it is necessaryto protect the passenger from the collision.
 2. The passenger protectionsystem according to claim 1, wherein, when the first detection digitaldata is different from the second detection digital data, and the firstbit sequence is equal to the second bit sequence, the electric controlunit compares the first or second detection digital data afterreplacement with a predetermined threshold digital data, wherein theelectric control unit determines that it is necessary to protect thepassenger from the collision when the first or second detection digitaldata after replacement is equal to or larger than the predeterminedthreshold digital data, and wherein all of bit values in thepredetermined threshold digital data other than the important bit groupare “0.”
 3. The passenger protection system according to claim 1,wherein the memory includes a first detection digital data memory, asecond detection digital data memory, a first bit sequence memory and asecond bit sequence memory, wherein the memory stores the detectiondigital data doubly in such a manner that the first detection digitaldata is stored in the first detection digital data memory, and thesecond detection digital data is stored in the second detection digitaldata memory, wherein the memory stores the bit sequence doubly in such amanner that the first bit sequence is stored in the first bit sequencememory, and the second bit sequence is stored in the second bit sequencememory, wherein the electric control unit retrieves the first detectiondigital data from the first detection digital data memory via a firstdata passage, and the electric control unit retrieves the seconddetection digital data from the second detection digital data memory viaa second data passage when the electric control unit compares the firstdetection digital data with the second detection digital data, andwherein the electric control unit retrieves the first bit sequence fromthe first bit sequence memory via the first data passage, and theelectric control unit retrieves the second bit sequence from the secondbit sequence memory via the second data passage when the electriccontrol unit compares the first bit sequence with the second bitsequence.
 4. The passenger protection system according to claim 3,wherein the sensor outputs the bit sequence together with the detectiondigital data as one data frame, wherein the detection digital data is a10-bit data, and wherein the bit sequence is a 4-bit data.
 5. Thepassenger protection system' according to claim 4, wherein the sensor isan acceleration sensor, a pressure sensor or a displacement sensor, andwherein the passenger protection device is an air bag device or a seatbelt pretensioner.
 6. The passenger protection system according to claim5, wherein, when the first detection digital data is different from thesecond detection digital data, and the first bit sequence is equal tothe second bit sequence, the electric control unit compares the first orsecond detection digital data after replacement with a predeterminedthreshold digital data, wherein the electric control unit determinesthat it is necessary to protect the passenger from the collision whenthe first or second detection digital data after replacement is equal toor larger than the predetermined threshold digital data, and wherein allof bit values in the predetermined threshold digital data other than theimportant bit group are “0.”